# The GALAH survey: unresolved triple Sun-like stars discovered by the Gaia mission

## TL;DR

This study uses Gaia data and a novel synthetic spectrum method to identify unresolved triple Sun-like star systems, revealing their prevalence and orbital configurations.

## Contribution

Developed a data-driven approach to detect unresolved multiple star systems by synthesizing spectra and photometry, uncovering new triple star candidates among Solar twins.

## Key findings

- Identified 6 definitive triple star candidates.
- Discovered approximately 2% of Sun-like stars are unresolved triples.
- Validated the method by assessing multiplicity in other stellar types.

## Abstract

The latest Gaia data release enables us to accurately identify stars that are more luminous than would be expected on the basis of their spectral type and distance. During an investigation of the 329 best Solar twin candidates uncovered among the spectra acquired by the GALAH survey, we identified 64 such over-luminous stars. In order to investigate their exact composition, we developed a data-driven methodology that can generate a synthetic photometric signature and spectrum of a single star. By combining multiple such synthetic stars into an unresolved binary or triple system and comparing the results to the actual photometric and spectroscopic observations, we uncovered 6 definitive triple stellar system candidates and an additional 14 potential candidates whose combined spectrum mimics the Solar spectrum. Considering the volume correction factor for a magnitude limited survey, the fraction of probable unresolved triple stars with long orbital periods is ~2 %. Possible orbital configurations of the candidates were investigated using the selection and observational limits. To validate the discovered multiplicity fraction, the same procedure was used to evaluate the multiplicity fraction of other stellar types.